High-temperature mechanical properties and fracture mechanism of A6B2O17 (A= Hf, Zr; B= Ta, Nb) high-entropy ceramics
Jing Wu, X.P. Hu, Shiyu Liu, Q. Liu, Jinping Guo, Shiliang Wang, Shuang Han, Wang Zhu
Abstract
A 6 B 2 O 17 (A= Hf, Zr; B= Ta, Nb) high-entropy ceramics are prepared by a solid reaction method, and the temperature-dependent mechanical properties are in situ determined by a high-temperature three-point bending combined with the digital image correlation method. The results show that (Hf 1/2 Zr 1/2 ) 6 (Ta 2/3 Nb 1/3 ) 2 O 17 (H 1 Z 1 T 2 N 1 ) ceramics exhibit superior high-temperature mechanical properties. As the temperature increases from 25 °C to 1200 °C, the fracture toughness and fracture strength decrease from 3.19 MPa·m 1/2 to 2.37 MPa·m 1/2 and from 97.38 MPa to 72.48 MPa, respectively. The H 1 Z 1 T 2 N 1 ceramics still maintain impressive mechanical properties at high temperatures due to the moderate grain size, low porosity and intergranular fracture . Furthermore, the higher entropy (9.61 R J/mol·K) of this ceramic leads to a significant high entropy effect, and the lattice distortion effects cause high-density dislocation regions, inducing a dislocation toughening mechanism.